Malodorous emissions from open organic slurry storage structures are a nuisance for nearby receptors. Large scale livestock facilities and subsequent malodorous gas emissions therefrom have become a source of national controversy.
Many methods have been tried to control malodorous emissions on open organic slurry storage basins: impervious covers with and without gas collection systems, bioaugmentation, chemical additives, enzymes and full and partial aerobic treatment systems. Impervious cover systems are quite costly and gas collection systems require significant initial capital investment as well as ongoing maintenance expense. Bioaugmentation, chemical additives and enzymes have not delivered consistent odor control and usually require significant ongoing labor and maintenance costs in addition to product costs. Aerobic methods work most convincingly, but excessive cost has prevented widespread acceptance of aeration as the preferred method of odor control. Floating biomats of straw provide partial aeration, have performed well and are reasonably economical. But it is difficult to place and maintain a solid straw cover on areas greater than two hundred feet wide. They also require regular maintenance to cover an increasing slurry storage surface area as sloped earthen basins fill, and to fill holes that appear as straw sinks to the bottom of the basin. Crossover piping and recycle pumps and plumbing have been clogged with sunken straw, potentially compromising basin capacity and requiring additional manpower to periodically unclog problem appurtenances. Sinking straw also increases organic loading in the basin, potentially compromising design storage capacity.
The invention relates to a cover system for an organic waste storage lagoon, as well as a method for construction of a cover and a method of deploying it over an at least partially filled organic waste storage lagoon. A cover is fabricated from a geotextile material that can be a polypropylene fiber, non-woven, needle punched fabric stabilized to resist degradation due to ultraviolet light exposure. The cover can be constructed from a plurality of panels of geotextile material that are connected edgewise as they are laid out in fanfold fashion along an edge of a lagoon basin. The cover system can include deployment ropes attached to the cover having a length sufficient to span the basin and engage a pulley system to pull the cover across the surface of material in the basin. Tether lines are attached to the cover and are connectable to anchoring structure along side the basin in order to secure the floating cover in place on the surface of material contained in the lagoon basin. The cover is effective to reduce malodorous gas emissions by 60% to 90%. The cover fabric is porous and it restricts the release of gas to a volume regulated by this porosity. Vapor pressure under the cover causes small areas of the cover to inflate and rise from the surface of the organic slurry in a low profile manner which creates a humid, aerobic environment along the unsubmerged surface of the cover. The anaerobic zone on the underside of the cover provides a substrate to which anaerobic bacteria attach and break down malodorous gases passing through the cover to the atmosphere.
An embodiment of the cover system includes a multiple strata cover. A top stratum is a sacrificial layer to shield the lower strata from ultraviolet light damage due to sun exposure. Lower strata include a non-woven, geotextile fabric layer and a flotation foam layer. The foam layer is comprised of foam strips that can either be placed on the bottom or sandwiched between the other two strata. The three strata are needle-punched together, using fiber stands from both the non-woven and sacrificial strata to bind all strata together.